LAUSR

Approximately 0·2–1% of routine RhD blood typings result in a “serological weak D phenotype.” For more than 50 years, serological weak D phenotypes have been managed by policies to protect RhD‐negative women of child‐bearing potential from exposure to weak D antigens. Typically, blood donors with a serological weak D phenotype have been managed as RhD‐positive, in contrast to transfusion recipients and pregnant women, who have been managed as RhD‐negative. Most serological weak D phenotypes in Caucasians express molecularly defined weak D types 1, 2 or 3 and can be managed safely as RhD‐positive, eliminating unnecessary injections of Rh immune globulin and conserving limited supplies of RhD‐negative RBCs. If laboratories in the UK, Ireland and other European countries validated the use of potent anti‐D reagents to result in weak D types 1, 2 and 3 typing initially as RhD‐positive, such laboratory results would not require further testing. When serological weak D phenotypes are detected, laboratories should complete RhD testing by determining RHD genotypes (internally or by referral). Individuals with a serological weak D phenotype should be managed as RhD‐positive or RhD‐negative, according to their RHD genotype.